Highly diastereoselective coupling reactions of enolates derived from butane-2,3-diacetal protected glycolic acids 1 and 2 and their alkylated derivatives with aldehydes are reported together with their efficient acid-catalysed deprotection to yield enantiopure anti-2,3-dihydroxyesters. A procedure to provide the corresponding syn-2,3-dihydroxyesters is also described in two cases, proceeding via an acylation–reduction sequence. An usual double addition reaction of butane-2,3-diacetal protected glycolic acid to small aliphatic acid chlorides provides a synthetically useful, densely-functionalised lactone after acidic deprotection.
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丁烷-2,3-二
缩醛保护的羟基酸1和2及其烷基化衍
生物与醛的高立体选择性偶联反应,并且有效的酸催化去保护反应能够生成对映体纯的反-2,3-二羟基酯。同时,在两种情况下也描述了一种提供相应顺-2,3-二羟基酯的程序,该程序通过酰化-还原序列进行。
丁烷-2,3-二
缩醛保护的羟基酸与小型
脂肪酸氯化物的常规双重加成反应在酸去保护后提供了一种合成上有用的、密集功能化的内酯。